May 2013
Problem of the Month

Sum-Thing Missing
by Ralph Fellows in GAMES

All 25 boxes in the square below contain whole numbers, but more than half of them are hidden from view.

The five numbers in each row add up to the same total, and the five numbers in each column also add up to that same total.

Can you figure out what number belongs in the square containing the question mark?

Solution to the Problem:

The number 5 belongs in the box with the question mark.

From the information given in the problem, the two rows containing the shaded boxes must add up to the same total as the two columns containing the shaded boxes.

Since the shaded boxes are part of both totals, they can be disregarded to create the equation:

14 + 2 + 20 + 10 + 23 + 11 = 25 + 16 + 12 + 13 + 9 + ?

Correctly solved by:

1. James Alarie	Flint, Michigan
2. Kalvin Hereford	Mountain View High School, Mountain View, Wyoming
3. Larissa Giessinger	Mountain View High School, Mountain View, Wyoming
4. Levi Harmon	Mountain View High School, Mountain View, Wyoming
5. Trenton Harmon	Mountain View High School, Mountain View, Wyoming
6. Dusty Iorg	Mountain View High School, Mountain View, Wyoming
7. Kyla Jo Hoopes	Mountain View High School, Mountain View, Wyoming
8. Brian Morrison	Thornton Academy, Saco, Maine
9. Serkan Samut	Blacksea Technical University. Trabzon, Turkey
10. Vikash Kumar	New Delhi, India

Send any comments or questions to: David Pleacher